My understanding was that you needed additional checks when the pricing condition is maintained - this is why I proposed to look into the BTE. Personally, I have not used it for this specific case, but from the explanation what the BTE is supposed to do, it seems like a possible solution. If for some reason the BTE does not perform as expected, probably your in-house developer can help you find out the reason.

Your requirement - to set the sales order to incomplete status once the maximum condition value is reached, is not how the functionality is supposed to work in standard: from what I know, the condition is applied until you reach the limit for value or number of orders, but the partial applying of the value (for example, if you have previously used up some of the discount in a sales order) or not applying the condition at all, does not lead to an incomplete document by itself.

I am not very convinced that it is a good idea to set the condition type as mandatory in the pricing procedure and try forcing document incompletion - after all, this is most probably some discount, agreed with a client, there is no reason to prevent additional orders without a discount from being processed. What is your exact business process? Are you trying to use this condition as some form of license or for product allocation purposes?